Process of drying lumber



F. K. FISH, In.

PROCESS OF-DRYING LUMBER.

APPLICATION FILED MAR-8, 1917. RENEWED DEC. 13,1919.

Patented Jan. 20, 19 20.

' of New York and State of UNITED STATES PATENT ornicn.

FREDERICK KJFISH, JR., OF NEW YORK, N. Y., 'ASSIGNOR TO LUMBER 'IIE ANDTIMBER VULCANIZING COMPANY, OF NEW YORK, N. Y.

Specification of Letters Patent.

Patented J an. 20, 1920.

Application filed March 8, 1917, Serial No.'153,489. RenewedDecember-13, 1919. Serial No. 344,751.

To allwhom it may concern:

Be it known that I, FREDERICK K. FIsH, J12, a citizen'of .the UnitedStates, residing at 2 Stone street, New York city, in the county NewYork, have invented-certain new and useful Improvements in Processes ofDryin Lumber, of which the following is a specification.

The present invention is based upon a proper recognition of the physicalcharacteristics of wood and analogous substances, the chemicalconstituency of their fluid content, andthe possibility of convertininto an agency for preservation, certain o their contained elements,which, under natural conditions, would form the basis of theirdeterioration or destruction but refers more particularly to wood.

structurally, wood consists of a skeleton of cellulose intermingledwithother organic substances, collectively designated as lignin, togetherwith a minor proportion of mineral matter or ash. Lignin, while notfully understood chemically, is closel allied to the cellulose elementof the woo and since it forms a part of the permanent structure of thewood, it may, for purposes of the present invention, be regardedidentical with the cellulose.

To utilize the natural bases of resin, acetic and tannic acid, existingin wood, as preservatives of the wood, it is necessary that they bedislodged from their cellular confinement, separated from their aqueoussolvent or vehicle, converted by oxidation and properly distributedthrough or deposited upon the cellular and fibrous structure of thewood.

I am aware that certain patents have been obtained for drying wood withfree steam, and heat under vacuum. By these methods wood may be driedbut they require such a length of time to accomplish an ideal anduniform product as to make them uncommercial, from a lumbermansviewpoint and cost such a large amount of money that such a processwould not have any commercial value. If the time required to treat woodunder such a process were reduced to a point where the methods wouldproduce an amount of wood which would make it of interest to the lumbermanufacturer, the heat in the sterilizer under the vacuum step would beof a degree that would cause the a furt er object is of time that onlythe surface moisture is removed and the resin and gums are distributedupon the fiber of the wood.

One of the objects of the herein set forth process is the reduction oftime required for dr 'ing wood and analogous substances;

the drying of certain destructible substances ate may be obtained. Astill further object is the treatment of wood in such manner as to fixtherein such natural properties of the wood as may be desirable.

The release and conversion of the properties especially the mostimportant of them, namely, the volatile oils which, when oxidized, formresin, is accomplished, according to my invention, by first placingthe-wood in a sterilizer which is metically closed; then introducinglive steam into the sterilizer under pressure; the temperature andpressure within the sterilizer varying according to the requirementsOfthe substance operated upon in such manner as to prevent injury to thematerial being treated, simultaneously introducing steam in the heatingcoils within the sterilizer until the desired temperature and pressureis obtained-and maintaining the temperature for such period of time asmay 'be found to be suitable to the material to be operated upon.

At the desired moment a vacuum is created within the sterilizer by theoperation of the vacuum pump. If it is advisable to obtain thedistillate, a surface condenser is preferable. Simultaneously, all meansused to bring the interior of the sterilizer under pressure are operatedin such manner and to such extent as is found desirable. The heat in thecoils may also be varied to such degree as may be found suitable. Theconnection with the condenser ermits the steam to flow away from thesteri izer, which tends to create a vacuum and reducesthe temperafromwhichthe distill-- capable of being herture therein. This induces arapid giving able that the transition from .ed, especially,

off of the vapor contained inthe substance",

depending upon the material being treated and the condition of themoisture contained therein. The heating fluids or gases are drawn out ofthe radiating pipes at this stage of the process and the material placedin a cooling shed, (not shown),-and subjected to a moderately heated,moist atmosphere until the temperature of the interior of the wood andthe surrounding atmosphere are harmonized.

Under certain conditions it may be desirpressure to vacuum be extremelygradual in order to maintain the desired conditions of the mediumsurrounding the material being treat with regard to the degree ofsaturation thereof.

By way of teaching the invention more in detail, one approved method ofpractising the same will be described with reference to the accompanyingdrawing, in which Figure I is a vertical longitudinal section of asterilizer, suitable for carrying out the steps of the process.

Fig. II is an end view, of the sterilizer.

Fig. III is a schematic view of the apparatus associated with thesterilizer for controlling it.

1 represents a sterilizer of construction suitable for containing waterat a temperature and under pressure considerably above the boilingpoint. It is preferably provided with a presser plate 2 with adjustingscrews 3, through means of which the char e of wood may be keptunderpressure whi e being treated. It is also provided with heating' coils 4,by which the temperature of the atmosphere or steam within thesterilizer may be heated to the desired degree; and with pipes 5.-whichmay be perforated for the purpose of supplying free st'eam within thesterilizer when desired. To equip the sterilizer 1 for convenientlydeveloping the several conditions incident to the difl'erent steps ofthe process, it is provided with an exhaust pipe 6 leading to a vacuumpump 7 with partly in section interposed condenser 8; 9 representstracks to receive the car or truck upon which the wood is loaded forintroduction in the sterilizer; 10 represents an escape valve.

In order that my process may be more fully and better understood, I willrecite in detail the several steps thereof in the drying of 1" x 2"requires from six to seven days, to dry in the ordinary kiln to shippingweight, which is about three-fifths of the weight of green wood. Thewood is firstplaced on a truck,

with stickers placed between the layers there-' of and run into thesterilizer 1. The sterirounded the cell walls or fibers now cypresslumber, which ordinarily lizer is then closed and steam is turned intothe heating coils at, say, one hundred pounds pressure. The drain orexhaust valve 10 leading from the sterilizer being opened,

steam is then gradually introduced into 7 sterilizer 1,'throughperforated pipes 5 until the wood is heated and the steam begins to passout through valve 10, valve 10 is then closed and the pressure in thesterilizer" raised t0,f say, thirty pou' as above atmosphere, thispressure being maintained for approximately one hour by admitting steamat thirty pounds pressure through perforated pipe 5. Then valve 10 isopened and the pressure in the sterilizer allowed to drop slowly andgradually, say, at the rate of three pounds per hour at the beginning ofthe said reduction of pressure, steam being crease of'pressure continuesthe rate thereof is reduced, say, when ten pounds above at- 0 mosphereis reached, the rate of decreased pressure is maintained at two poundsper hour. This reduction is continued until the pressure is reduced tosay, ten pounds, be-. low atmosphere, or five pounds absolute. At thestate of this final reduction of pressurea sliglft heating takes placeas a temperature I of say, 200 F. is maintained; the boiling point isabout 126 F. The heat is then cut off from, the heating coils, also thesteam from perforated pipes 5,, the vacuum is maintalned until the heatdrops below the saturation temperature, when the vacuum isv broken andthe wood placed in a cooling compartment, (not shown), ment beingpreferably provided with insulated walls and a moderately heated, moistatmosphere created therein in which the wood is allowed to remain untilthe interior temperature thereof and the surrounding atmosphere areharmonized.

The wood will now be thoroughly dried without removing the values of itssap; the latter will be converted especially as to its volatile oils,into resin; this resin having permeated the entire cellular structure ofthe wood, while the 'moisture was still present. and the pores opened upand temperature high, will have precipitated upon or surthat themoisturehas departed. Thus, the wood has been rendered homogeneous throughout,indurated, sterilized and rendered less hygro scopic and correspondinglyimmune from spores or. fermentation or the like. And all theseconditions are attained-without checking, warping, case hardeningor'other deterioration of the physical characteristics of the wood.

From the foregoing, it will be seen that said compart- 105 the firstessential condition to be produced is the thorough softening and openingup of the wood structure and the.dissolving of its gummy sap matters andfreeing them from their confinement; so that they can be distributedthrough the wood structure.

I claim 1. The process of drying wood, which consists in, surroundingthe wood by a body of live steam under pressure; then gradually reducingthe pressure while supplying heat; finally drying in a slightly heatedmoist atmosphere.

2. The process of drying wood, which consists in subjecting the wood tolive steam under pressure; then reducing the pressure to belowatmospheric pressure at the same time maintaininiglthe steam at asuper-heated temperature; ally drying the woodat atmospheric pressureand in the presence of a moderatel heated, moist atmosphere.

3; he process of drylng wood, which con-- the wood to a body ofsteam atsubstantially the dew point thereof sists in subjectm under pressure;then gradually reducing the pressure; finally drying in a, moderatelyheated atmosphere at atmospheric pressure.

4. The process of drying wood, which consists in subjecting the wood toa body of live steam under pressure; then withdrawing moisture therefromwhile decreasing the pressure; finally drying in a body of moderatelyheated, moist atmosphere at atmospheric pressure jandharmonizing thetemperature of the interior of the wood with the surrounding atmosphere,

In testimony whereof I'aflix my signature.

FREDERICK K. FISH, JR.

